The welfare effects of entry: the role of the input market

In a successive Cournot oligopoly, we show the welfare effects of entry in the final goods market with no scale economies but with cost difference between the firms. If the input market is very concentrated, entry in the final goods market increases welfare. If the input market is not very concentrated, entry in the final goods market may reduce welfare if the entrant is moderately cost inefficient. Hence, entry in the final goods market is more desirable if (1) the input market is very concentrated or (2) the cost difference between the incumbents and the entrant is either very small or very large. It follows from our analysis that entry increases the profits of the incumbent final goods producers if their marginal costs are sufficiently lower than the entrant's marginal cost.